Safety device for burners



y 30, 1933- E. R. SNAVELY 1,911,776

SAFETY DEVICE FOR BURNERS Filed Jan. 24, 1929 2 Sheets-Sheet l If I r a a I f 16 P /0 29 9 7g i 6 76a y /4 79 h if 4 I J Z////////////////7////// //'//4/!/ ////////7/A 3nvcntor Jar? Jame/Z final e4 M y 1933- E. R. SNAVELY SAFETY DEVICE FOR BURNERS 2 Sheets-Sheet 2 Filed Jan. 24, 1929 4 6 .6 z m //////////////////4423344442? f 1 e Z Z G w/ w 0 Q m 2 j k 9 3 Z 2 8 J v v W \\\\\.v\ N N v Gttorneg Patented May 30, .1933

UNITED STATES PATENT OFFICE EARL RUSSELL SNAVELY, 0F ROSELLE, NEW JERSEY, ASSIGNOR TO THE FIRE KING COMPANY, INC., 01' NEWARK, NEW JERSEY SAFETY DEVICE FOR BURNERS Application filed January 24, 1929. Serial No. 334,782.

This invention relates to a safety control device for stopping the supply of fuel upon failure of the fuel to ignite.

In the use of pulverized coal burners, o1l burners, gas burners, etc., it is extremely important that means .be provided for automatically cutting off the supply of fuel to the burner in case the fuel discharged from the burner fails to ignite, for if the fuel is not consumed as it is supplied by the burner, it will accumulate in and about the furnace in a highly inflammable condition. In case the fuel fails to ignite while the furnace is hot it is important that the deliverv of fuel be stopped quickly, as most fuels when delivered to a hot furnace tend to vaporize and become explosive in character. As usually some particle of carbon or point of the furnace remains hot enough to ignite such fuel after the flame fails, explosions may occur if the delivery is not stopped quickly. It is also desirable that once the supply of fuel to the furnace is stopped it shall not be resumed again, and ignition of the fuel shall not be attempted, until the furnace has had time to cool. and until the draft through the furnace shall have'in some measure diffused the supply of fuel, if any, which was injected into the furnace during the interval between the failure of the fuel to ignite and the stoppage of the supply.

It has been proposed heretofore to use a thermostat for cutting off the supply of fuel to a burner upon failure of the fuel to ignite, and by means of a so called fast switch for stopping the burner, and a slow switch for restarting the burner, and attempt has been made to provide an interval between the cutting off of the supply and the re-delivcry of fuel and renewal of the ignition.

Difliculty however has been experienced in developing a thermostat control which will operate promptly to cut off the fuel supply, due to the fact that if the thermostat is placed sufficiently close to the burner to operate promptly when the burner is started, it is likely to be injured by the heat of the furnace when the latter has reached its normal operat'ng temperature. And if the thermostat is-p aced in some position remote from orsheltered from the burner it will not operate promptly. This is especially objectionable in those thermostats or combination of thermostats providing for fast and slow switches, where the actual effectiveness of the thermostats depend on the action of the heat upon a coil or coils of bi-metallic thermostatic metal, hereinafter referred to as the thermostatic element; for if'the thermostats are placed close enough to the fire for the slow switches to act, or if they are placed in the path of hot combustion gases, there is a gradual deterioration in the metal of the thermostatic elements, proportional to the actual exposure of the metallic thermostatic elements to the heat or gases, and after a period of time the fast element has often so deteriorated that it operates slower than the slow element.

One important feature of the present invention therefore resides in a safety control thermostat that can be located near the burner, where it will be quickly heated and cooled as the flame ignites or fails, and in the construction for preventing the thermostat from becoming over heated.

Another important feature of the present invention resides in a safety control thermostat which incorporates the so-called fast and slow switches, but wherein said switches operate from one thermostatic element and in such manner that they will always continue to operate in the same relation to each other, namely,"the fast switch will always be faster than the slow switch.

Another feature of the invention resides in a thermostat in which as one face of the thermostatic element'or coil is exposed to a cooling medium, and the other to heat by conduction, convection and radiation, in creased act-ion can be obtained quicker and with less temperature change.

In the accompanyingdrawings, Figure 1 is aside view, partly in section of the thermostat;

Figure 2 is a transverse sectional view of the device along the line aa' of Fig. 1, showing the fast and slow switches on one position;

Figure 3 is a similar view showing the switches in another position;

Figure 4 is an end view of the device; Figure 5 is a fragmentary longitudinal 5 section of the shaft; and

Figure 6 is a longitudinal view partly in section of the shaft.

In the illustrated embodiment of my invention, 21 is a bracket which may be mounted on any convenient opening to the firebox of the furnace, such as the firing door, the clinker door, etc, and should be mounted in such manner that the thermostatic element will. receive heat directly from the flame of the burner, although under usual conditions, the element should not be mounted in the flame itself. 23 is a helical coil of bi-metallic thermostatic metal with the slow expanding metal on the inside of the coil, and I refer to it hereafter as the thermostatic element. 5 is a hollow shaft closed at the ends, and for convenience I refer to the end which extends into the furnace and to which 23 is attached as the inner end. 25 is a screw to attach one end of 23 to 5. 24 are holes or ports from the hollow center 31 of the shaft 5, and decrease in size and number as they extend outward along shaft 5, there being none except where 5 is surrounded by the thermostatic element 23. 22 is a screw to attach theother end of 23 to 20. 20 is a combined bushing and bracket made of lava, stone, porcelain, or other suitable material which is highly resistant to the action and conduction of heat. It forms a bracket or fitting to attach the thermostat to the furnace, by meshing with and fitting through an opening in bracket 21. 18 is acollar which is rigidly attached to the shaft 5 by the screw 19. 14 is a bracket which is frictionally mounted on the shaft 5, and which carries the mercury switch 8. 9 is a clamp fastening8 to 14 by means of the screw 10. 28 is a collar or disk of friction material which is free to move on shaft 5 in a longitudinal direction, but is keyed to 5 by a lug 29 which fits into a slot 30 in 5, so that 28*? and 5 rotate together. 28 is pressed against 14, and presses 14 against 18 in such manner as to cause 14 to revolve with them and with shaft 5, when 14 is free to rotate. 13 is a stud or lug on the case 17 of the thermostat, which limits the movement of bracket 14. 16 is a spring which holds collar 28' against 14. 15 is a collar or washer against which springs 16 and 16 press. 6 is another collar somewhat similar to 18. and is attached to 5 by screw 7. 11 is another bracket mounted frictionally on 5 to revolve with 5 when free, but to remain stationary as 5 revolves when the movement of 11 is limited by the stud or raised spot 12 of the thermostat casing 17. 28 is a friction collar or disk similar to 28" and like 28 is keyed to shaft 5 by lug 29 fitting into slot 30 in such manner that it is free to move on 5 longitudinally, but revolves with 5. 16 are springs ressing 28 against 11. It should be noted that the movement of the bracket 11 is so limited b the lug 12 that it moves through a very mucli smaller are than bracket 14. 3 is an opening to the inside 31 of the hollow shaft 30. 1 is a cap which is threaded to fit spiral threads or screws on 5. The apparatus is found to work well when the pitch of these threads is steep. 2 is a spring which is attached to 1, and which fits into depressions 26 in the back cover 4 of the thermostat, and operates to prevent 1 revolving with shaft 5, yet. allows longitudinal movement of 1 on 5.

\Vhen used with mercury switches, the shaft 5 must always be mounted exactly horizontal, and the studs 12 and 13 should be exactly above and below the shaft 5.

If the thermostat is mounted so that the thermostatic element 23 extends into the fire box of a furnace, when the burner starts, as the fuel is ignited, thermostatic element 23 distorts to turn shaft 5. Shaft 5 rotates in bushing 20 and turns collars 18 and 6, and disks 28 and 28. Considering the positions of 14 and 11 as shown in Fig. 2 as being their cold position, and that shaft 5 turns counter-clockwise as element 23 heats, bracket 14 and bracket 11 will start to revolve with shaft 5. If the mercury switches on 14 are more nearly horizontal than those on 14, as shaft 5 revolves they will pass the horizontal positions first, and will operate first. Moreover, the proportional times of their operation will depend on the angles at which they are mounted, and can be varied by varying the angles of their mountings. The lug 12 however interrupts the rotation of 11 very shortly after the switch 8 passes the horizontal position, and 11 starts to slip on the shaft 5, as 5 continues to revolve. 14 however is so designed that the Pug 13 only interrupts its travel after it has rotated through a wide arc, and 14 continues to revolve with 5 until the brackets are in the position shown by Fig. 3, at some point in its travel having operated the switch 8", de pending on the angle mounting of 8.

As 5 has been revolving, it has been unscrewing the cap 1, for 1 cannot revolve automatically with 5 because spring 2, attached to 1, is fitting into one of the depressions on the back of back cover 4, as shown in Fig. 4. As 5 continues to revolve and unscrew 1, the port or opening 3 into the hollow center of shaft 5 is uncovered. \Vith 3 open, air now flows through 31 and out the air conducting conduits or ports 24, cooling the shaft 5 as it flows through. Also, this air, striking the thermostatic element 23 on its inner face, the face which has the lower coefficient of expansion, cools this face,

causing a relative contraction of this face, and the action of the thermostatic element is increased, without the temperature of the element beingincreased., Also, the element will be maintained at a relatively low temperature, for the inflow of cold air will not only tend to cool 23, but will tend to keep the hot gases away from 23. Therefore, the heat whlch 23 will receive from this time on' y gresslvely toward the inner end of the shaft.

will be largely radiant heat. By properly proportioning the sizes of the air-conducting conduits 24 to their location on the shaft 5, and to the cooling effect re uired, an effect will be maintained proportional to the exposure of 23 to heat, and all points of 23 will be maintained at approximately the same temperature. Thus every part of 23 will be workin at the same elliciency, and no part of it Wlll need to become very hot, even thou 'h considerable rotation of 5 is desired. Xlso, since the port 3 opens as 5 turns, the initial movement of 5 will take place very quickly indeed, but greater movement will be slower. i

When the heat to which 23 is exposed decreases or ceases, the thermostatic. element will revolve the shaft 5 in the opposite direction, and since the heat is largely radiant,

any stoppage of the flame will cause a very quick change in the temperature of 23, with a corresponding quick movement of shaft 5. As shaft 5 revolves, it will turn with its brackets 11 and 14. Since bracket 11 has moved through a shorter arc than bracket 14, and sinceswitclies 8 and 8' are near the horizontal, the will act very quickly. The natural rate 0 cooling of 23 will morever be greatly speeded up by the flow of cold air from the ports of 24. As further movement of 5 tends to. sc rew on the cap 1 and close the port 3,.cuttingofi the supply of air from the ports .24, the-"coil :,23j will tend to cool more slowly, giving a slower movement to the wide swinging bracket 14, and delay in still more the action of the switch 85 The thermostat lends itself readilyto alprising a helical thermostatic element adapted to be exposed to heat and a hollow shaft forming a support for said element, said shaft being provided with a plurality of lateral apertures disposed longitudinally of said helical element to direct a cooling fluid thereon.

2. In a thermostat device as set forth in claim 1, said apertures increasing in size prov 3. Athermostat device as set forth in claim 1, and means actuated by the thermostat for automatically regulating the supply of said cooling medium.

4. In a thermostat forburners, a thermostatic element formed of a helical coil of thermostatic material, with the material having the lower coefficient of expansion wound on the inside of the coil, and air-conducting conduits extending within the coil for directing a cooling medium against the inside of the coil.

5. A thermostatic device as set forth in claim 4 and means for automatically varying the supply of cooling medium in accordance with the changes in temperature to which'the element is subjected.

6. In a thermostat device for burners, a

thermostatic element, means for subjecting said element to a cooling medium, and means actuated by the thermostatic element for varying the amount of said cooling medium in accordance withthe variations in the temperature to which the element is subjected.

7. In a thermostat for burners, a thermostatic element exposed to heat increasing in intensity toward the exposed end, and a hollow support provided with apertures graduated in size for projecting a cooling medium against said element in amounts varying progressively along the element to thereby equalize thetemperature of the element throughout its length.v

EARL RUSSELL SNAVELY.

most any control circuit for burners, by the variation of the. number, direction of swing, I

and type of switchused. Forexample, in Patent No. 1,583,586, isued Mav 4.1926 to Fischer et a1, if switches of the" mercury tube type having two electrodesv in each end are substituted for those shown in my draw ings, and if they are mounted with their angles from the horizontal and their direction of rotation properly arranged, the ther-. mostat will function perfectly. Or if the tube having four electrodes in my application for patent dated December 28,1926,

Serial No. 157,581, is substituted for tube '8, and if the other tubes are arranged on 11 and 14 correctly, the thermostat will function.

What. I claim is:-

1. A thermostat device for burners, com- 

